The present invention relates generally to an anti-lock braking system (ABS) and, in particular to an anti-lock braking system wherein a single electronic control unit (ECU) can be used with alternative ABS arrangements and configurations.
Anti-lock braking systems function to prevent the locking of individual wheels of a vehicle while the vehicle is braking, and thus to shorten the braking distance of the vehicle while maintaining lateral traction, particularly when braking on smooth road surfaces. In order to brake a utility vehicle such as a truck, tractor, trailer or the like, a braking medium, such as compressed air, is normally injected at a controlled rate into the brake cylinder, thus actuating the respective wheel brakes. In brake units equipped with anti-lock braking systems, braking-pressure modulators (e.g. solenoid valves) are incorporated into the pneumatic lines. The modulators can be actuated by an ABS electronic control unit to decrease, maintain or increase the braking pressure. Accordingly, the modulators each contain one inlet valve (for increasing pressure) and one outlet valve (for decreasing pressure).
There are a number of distinct anti-lock braking systems known within the art. Utility vehicles can have one, two, three or more axles. Typically, two wheels are allocated to each axle, although more may be provided. These wheels may or not be sensed (i.e., equipped with wheel-speed sensors). Each wheel brake may be provided with its own modulator, or one common modulator may serve multiple wheel brakes corresponding to an axle. A common modulator ensures that both wheels of an axle receive the same braking pressure. There are several anti-lock braking regulation schemes that are known within the art. These regulation strategies include select-low regulation (SL), select-high regulation (SH), modified axle regulation (MAR) (see, for example, German Patent 37 22 801), and variable axle regulation (VAR) (see, for example, German Patent 197 23 323).
There are two anti-lock braking systems which are most common for utility vehicles with two axles (a front axle which may be articulated and a rear axle).
The first common system consists of four wheel-speed sensors and four braking-pressure modulators (i.e., one wheel-speed sensor and one braking-pressure modulator for each wheel). This system is known as individual regulation (IR), as each of the wheels of the vehicle can be regulated individually. The system is also known as the 4S/4M system, corresponding to the number of wheel-speed sensors (S) and the number of braking-pressure modulators (M).
The second common anti-lock braking system for a two-axle utility vehicle consists of four sensors and only three modulators and is known as a 4S/3M system. In 4S/3M systems, one of the axles is equipped with two modulators, while the brake cylinders of the other axle are supplied commonly by a single modulator, via what is known as a common axle modulator. The commonly supplied axle can be either the front or rear axle of the vehicle (see WABCO ABS/ASR Brochure xe2x80x9cDxe2x80x9d-xe2x80x9cCABxe2x80x9d Version, August 1999, p. 9).
A third, less widely used, system for two-axle utility vehicles consists of four wheel-speed sensors, but only two modulators (4S/2M). In 4S/2M systems, each axle is supplied commonly by one axle modulator.
Various embodiments of electronic ABS control units are known for the aforementioned three systems: specifically, ECUs with four regulating channels for the 4S/4M system, ECUs with three regulating channels for the 4S/3M system, and ECUs with two regulating channels for the 4S/2M system. In this context, a regulating channel is the components and signals between the wheel speed sensor and an output amplifier or end stage of the modulator for a wheel. These known embodiments of electronic ABS control units are similar in design, the only difference being that the respective unnecessary end stages are not included in the 4S/3M and the 4S/2M versions (i.e., these have only two or three end stages instead of the four end stages in a 4S/4M system).
Further variations of the ABS electronic control units include systems where the individual axle modulator is disposed on the front or rear axle of the vehicle. The previously listed regulation schemes known as MAR and VAR also multiply the number of possible versions of the ABS electronic control units (e.g., a 4S/3M anti-lock braking system may employ either MAR or VAR).
A consequence of the number of distinct and incompatible ABS electronic control units is that it becomes necessary to maintain a large inventory of different versions of ABS electronic control units. As a result, higher production and warehousing costs are incurred. This is especially problematic when individual versions are sold only in limited quantities.
In certain situations, the known 4S/3M ABS electronic control units may be installed mistakenly in a vehicle equipped with a 4S/4M ABS system. If such a 4S/4M vehicle is properly connected via the associated cable harness to the 4S/3M electronic control unit, the electronic control unit recognizes the superfluous modulator and transmits an error signal. The plug-and-socket connector between the cable harness and the ABS electronic control unit is the same for both systems. If, however, the connecting plug for the fourth modulator is not inserted, the 4S/3M electronic control unit would only detect three modulators, and thus would erroneously recognize a valid system and deliver unsuitable regulating signals (SL) for the second modulator of the axle during regulated braking. As a result the vehicle may not brake properly.
Accordingly, it is desired to provide an improved ABS electronic control unit that is compatible with a variety of anti-lock braking systems and eliminates the need for maintaining a large inventory of different ABS electronic control units for the multitude of anti-lock braking systems. It is also desired to provide an improved anti-lock braking system that eliminates the above described risks from mismatching vehicles with incompatible ABS ECUs.
An anti-lock braking system, method, and an electronic control unit are provided that allow for the use of a single electronic control unit in a variety of anti-lock braking systems and obviate the shortcomings in the prior art.
In a first aspect of the present invention, an anti-lock braking system is provided for wheeled vehicles having multiple axles. The system includes at least one modulator per axle coupled to at least one brake cylinder for controlling braking pressure. The system also includes wheel-speed sensors, and a multi-channel electronic control unit for selectively controlling the modulators. At least one modulator may be commonly activated by two channels of the electronic control unit.
In another aspect of the present invention, an electronic control unit having multiple channels for controlling an anti-lock braking system including modulators, speed sensors, and means for coupling the modulators and speed sensors to the electronic control unit such that two channels of the multiple channels control a single modulator is provided. The electronic control unit comprises programmable storage means for recognizing the type of anti-lock braking system to which it is coupled based on the means for coupling.
In yet another aspect of the present invention, a method for controlling an anti-lock braking system having speed sensors and modulators coupled to an electronic control unit having multiple channels, each channel having at least one end stage is provided. The method comprises the steps of recognizing the type of anti-lock braking system that the electronic control unit is coupled to and selecting an anti-lock braking regulation scheme based on the recognized type of anti-lock braking system.
The present invention provides an improved anti-lock braking system and ECU that is compatible with a variety of anti-lock braking systems and eliminates the need to maintain a large inventory of different ABS ECUs for the multitude of ABS systems. Accordingly, the inventory, production, warehousing and other costs of maintaining multiple versions of ABS electronic units are eliminated. The present invention also provides an improved anti-lock braking system that eliminates the above described risks from mismatching vehicles with incompatible ABS electronic control units.
Accordingly, it is an object of the present invention to provide an improved anti-lock braking system and method.
Another object of the present invention is to provide an electronic control unit which can sense the type of anti-lock braking system to which it is coupled and react accordingly.
Another object of the present invention is to provide an anti-lock braking system equipped with such an electronic control unit.
A further object of the present invention is to provide an anti-locking braking system which overcomes the problems associated with the prior art.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The present invention accordingly comprises the various steps and the relation of one or more of such steps with respect to each of the others, and embodies features of construction, combinations of elements, and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.